1. Field of the Invention
The present invention relates to a method of selecting a polypeptide sequence which imparts a target substance binding-ability to a protein of interest and a nucleic acid construct using therefor. The present invention also relates to a peptide that binds specifically to a metal oxide or a silicon-containing compound, and a method of producing a fusion protein using the peptide, a method of purifying the fusion protein, a method of immobilizing the protein, as well as a surface treatment agent for biomaterials and the like.
2. Brief Description of the Related Art
The term “peptide aptamer” is a general term for an artificial peptide that binds specifically to a specific target molecule. At present, not only does a peptide aptamer exhibiting a binding function similar to an “antibody” draw much attention as a probe for molecular detection in the field of chemistry, biology, and medical science; but also is anticipated in the field of medicine as a molecular target drug for the next generation in place of an antibody pharmaceutical.
In order to obtain peptide aptamers that bind specifically to a specific target molecule, screening for the peptide aptamers is carried out by repeating a cycle composed of: expressing random polypeptides from DNAs encoding the random polypeptides; bringing them into contact with target molecule; selecting one that binds specifically to the target molecule; and amplifying a DNA which encodes it.
For such a screening, a technique such as phage display (G. P. Smith et al. (1985) Science, vol. 228, p. 1315-1317), ribosome display (JP3127158B, JP2001-521395A, JP2002-500514A, WO 01/75097, and J Hanes and A Pluckthun (1997) Proc Natl Acad Sci USA, vol. 94, p. 4937-4942), or mRNA display (L. C. Mattheakis et al. (1994) Proc Natl Acad Sci USA, vol. 91, p. 9022-9026, R. W. Roberts et al. (1997) Proc Natl Acad Sci USA, vol. 94, p. 12297-12302 and N. Nemoto et al. (1997) FEBS Lett., vol. 414, p. 405-408) has been employed. A polypeptide selected by a screening method using such a display technique comes with genetic information encoding its amino acid sequence, and thus the selected polypeptide can be promptly amplified in large amounts by genetic engineering process based on the genetic information encoding it. In addition, by analyzing the genetic information, the amino acid sequence can be readily identified.
Development of the display technique described above has made it possible to screen a target substance binding peptide efficiently. However, when a target substance binding-ability is imparted to a protein of interest by fusing the obtained target substance binding peptide to the protein of interest, it has often happened, albeit depending on the type of protein, that the fusion protein does not show the target substance binding-ability due to problems concerning spatial structures and the like.
Meanwhile, a metal oxide and a silicon-containing compound have been recently drawn much attention as medical materials. In view of this, it is considered that obtaining a peptide that binds specifically to a metal oxide or a silicon-containing compound allows various modification of the surface of medical materials containing a metal oxide or a silicon-containing compound, which is useful for providing the medical materials with multiple functions.
The present inventors have reported a peptide having a histidine-rich amino acid sequence as the peptide that binds specifically to a metal oxide or a silicon-containing compound (JP 2009-136280A). In addition, a titanium dioxide binding peptide TBP-1 has been reported in K Shiba et al., Langmuir (2005), vol. 21, p 3090, and K Shiba et al., Nano Lett. (2006), vol. 6, p 515.